Capacitors have undergone substantial improvement over the years. Smaller capacitors are in demand for various applications. One such application is for biomedical implants. For example, defibrillators and pacemakers use capacitors for pulse delivery.
The defibrillator or cardioverter includes a set of electrical leads, which extend from a sealed housing into the walls of a heart after implantation. Within the housing are a battery for supplying power, monitoring circuitry for detecting abnormal heart rhythms, and a capacitor for delivering bursts of electric current through the leads to the heart.
The capacitor can take the form of a flat aluminum electrolytic capacitor. Flat capacitors include a stack of flat capacitor elements mounted within a capacitor case. Each flat capacitor element includes one or more separators between two sheets of aluminum foil. One of the aluminum foils serves as a cathode (negative) foil, and the other serves as an anode (positive) foil. The capacitor elements each have an individual capacitance (or energy-storage capacity) proportional to the surface area of the foil.
One drawback in manufacturing such capacitors is that each of the anodes and each of the cathodes must be connected together. For instance, all the anodes are crimped or welded together and attached to a feedthrough terminal for connection to circuitry outside the capacitor case. Another process is also done for the cathode foils in the capacitor stack. Errors during the manufacturing steps may cause defects in the capacitor or decrease the reliability of the capacitor after it is constructed. Another drawback is that the interconnections take up space within the capacitor. This increases the size of the capacitor, which is undesirable when the capacitors are used for implantable medical devices such as defibrillators.
Thus, what is needed is a simple way to provide the anode and cathode interconnections of capacitors with as few steps as possible and which lends itself to mass producing said capacitors.